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PubMedDate not supplied

Biopharmaceutical evaluation of time-controlled press-coated tablets containing polymers to adjust drug release.

This paper deals with press-coated modified release tablets in which the drug dose is situated in the core or is divided between the core and the coat. The coat contains polymer (sodium alginate or hydroxypropylmethyl cellulose, HPMC) to control drug release. The main objective was to investigate how the pharmacokinetic profile of the model drug could be modified by altering the proportion of the drug between the core and the coat. The effect of the amount of the polymer in the coat was also studied. Bioavailability tests were carried out on healthy volunteers. In the absorption curves of the tablets containing 50%, 67% and 80% of the drug in the core and 180 mg HPMC in the coat a bimodal profile was observed. No bimodal release pattern in the in vitro dissolution studies was found. If the whole dose was incorporated in the core the absorption curve has only one clear t(max) value at about 10 h. Doubling the amount of HPMC in the coat dramatically decreased drug absorption. It was concluded that, if a slightly reduced t(max)-value was required, the viscosity grade of HPMC used should be lowered.

Adult↗
PubMed1996

Gelatin microspheres: influence of preparation parameters and thermal treatment on chemico-physical and biopharmaceutical properties.

The aim of this paper was to investigate the influence of preparation parameters on gelatin microspheres production, chemico-physical characteristics and drug encapsulation. In particular, we focussed our attention on the manufacturing parameters such as amount of polymer, stirring speed, presence and concentration of surfactants. As model drugs, TAPP-Br, clonidine hydrochloride and bromocriptine mesylate were chosen in order to compare their encapsulation and release characteristics with microspheres. In the second part of this work, a study of the influence of thermal treatment on the microspheres is reported, performed with the aim to possibly modify gelatin dissolution and drug release. In particular, the effect of this treatment was evaluated on microsphere characteristics such as swelling, porosity and dissolution, and finally on the release profiles of the encapsulated drugs.

Adrenergic alpha-Agonists↗
PubMed1985

Biopharmaceutical test of ocular irritation in the mouse.

A simple and accurate test for ocular irritation in mice has been developed in which the subjective evaluation of intolerance is supplemented by an objective measurement, based on the change in corneal permeability following ocular damage. An episcopic microscope is used to detect, under blue light, the amount of fluorescein that diffuses across the inflamed or damaged cornea. The fluorescence emitted by this fluorochrome is quantified by a photomultiplier. The degree of ocular damage is expressed as a fluorescence index which can be subjected to statistical analysis. In a first stage of this study a series of surfactants has been examined and classified on the basis of their fluorescence index. The classification thus obtained is in agreement with those previously reported in the literature for assessment of ocular irritation by other methods.

Animals↗
PubMed1988

Biopharmaceutics, pharmacokinetics and pharmacology of psoralens.

The psoralen derivative 8-methoxypsoralen (8-MOP) and to a lesser extent some other psoralens, including 5-methoxypsoralen (5-MOP) and 4,5',8-trimethylpsoralen (TMP) have acquired a place in the treatment of psoriasis and other dermatoses. They are only active when combined with long-wave ultraviolet light: PUVA therapy (Psoralen plus UVA). Successful PUVA therapy depends on sufficiently high psoralen concentrations coinciding with the time of irradiation. The use of oral or rectal pharmaceutical formulations with 8-MOP dissolved in liquid is preferable to conventional tablets or capsules. Since no formulation of 5-MOP with fast and predictable absorption is available 8-MOP should be preferred in PUVA therapy. The effectiveness of oral TMP is doubtful, because of low serum concentrations, probably due to malabsorption.

Animals↗
PubMed1993

High-performance liquid chromatographic determination of bupivacaine in plasma samples for biopharmaceutical studies and application to seven other local anaesthetics.

A sensitive analytical procedure for bupivacaine dosing in plasma samples by reversed-phase high-performance liquid chromatography is described. After a two-step extraction, the analysis was performed using a C18 column and a mobile phase of 0.01 M sodium dihydrogen-phosphate (pH 2.1)-acetonitrile (80:20, v/v). The extraction yield of bupivacaine from plasma was 73.5 +/- 5.1% (mean +/- S.D., n = 10). The within-day and between-day reproducibilities at a concentration of 100 ng/ml were 2.1% and 5.6%, respectively (n = 10). Calibration curves were linear (r2 = 0.9996) between 5 and 1000 ng/ml. The limit of detection, defined by a signal-to-noise ratio of 3:1, was 2 ng/ml. The accuracy at a concentration of 100 ng/ml was 2.3%. This method could be applied to the plasma analysis of seven other local anaesthetics (articaine, etidocaine, lidocaine, mepivacaine, pramocaine, procaine and tetracaine). The procedure was used in bioavailability studies of bupivacaine-loaded poly(D,L-lactide) (i.e. PLA) and poly(D,L-lactide-co-glycolide) (i.e. PLGA) microspheres after subcutaneous and intrathecal administrations in rabbits.

Anesthetics, Local↗
PubMed1995

Improved reversed-phase high performance liquid chromatography columns for biopharmaceutical analysis.

Reversed-phase high performance liquid chromatography continues to grow in importance for the analysis of peptides and proteins in biomolecular and pharmaceutical research. The mobile-phase conditions for separation of proteins and peptides are essentially fixed. Most separations of these solutes are conducted with shallow gradients using aqueous buffers modified with acetonitrile. Therefore, changing selectivity in peptide and protein separations is often best accomplished by a change in bonded-phase chemistry of the column (e.g. by using CN- or C3-bonded phases rather than C8 or C18). In general, however, short-chain bonded phases are more unstable and irreproducible than bonded phases having longer chains, due to increased susceptibility to hydrolysis as hydrophobicity of the bonded phase decreases. These problems are minimized using bonded phases that are protected through use of sterically bulky side-groups (StableBond Technology). This paper describes a series of comparisons between traditional polymeric bonded-phase silica columns and sterically protected, highly purified, silica stationary phases. These studies compare lot-to-lot reproducibility, stability of the bonded phase, selectivity effects between bonded phases, and operational advantages that can be obtained by high temperature operation using a series of stable bonded phases.

Chemical Phenomena↗
PubMed2004

The use of asymmetrical flow field-flow fractionation in pharmaceutics and biopharmaceutics.

Field-flow fractionation (FFF) is a family of flexible analytical fractionating techniques which have the advantage that the separation of analytes is achieved, solely through the interaction of the sample with an external, perpendicular physical field, rather than by the interaction with a stationary phase. The rapid progress in pharmaceutical biotechnology goes along with an increasing demand in potent, high-efficient analytical methods. Thus, FFF techniques are gaining increasing attention for their ability to separate and characterize populations of polymers, colloids and particles of up to about 100 microm in size. It is the intention of this review to provide an overview on common FFF techniques, to summarize inherent advantages and limitations and to introduce both established and challenging applications in the (bio)pharmaceutical field. Thereby, asymmetrical flow FFF is addressed predominantly, since it is the most versatile applicable FFF technique.

Biological Products↗
PubMed2004

Improvement of warfarin biopharmaceutics by conjugation with poly(ethylene glycol).

One of the most used and useful polymers, poly(ethylene glycol) (PEG) was used as a carrier for warfarin. The drug-polymer conjugate was freely water soluble at room temperature. The hydrolytic stability of the PEG-warfarin was investigated at physiological pH and confirmed the stability of the conjugate. In vivo release studies demonstrated a good release of parent drug, without the initial high plasma level of warfarin.

Administration, Oral↗
PubMed2006

Drug absorption in the elderly: biopharmaceutical considerations for the antiepileptic drugs.

The management of antiepileptic drug (AED) pharmacokinetics remains a challenge in the treatment of patients with epilepsy. Drug characteristics, such as protein binding, mechanisms of drug elimination, and the potential for pharmacokinetic/pharmacodynamic interactions, are important considerations for drug selection and may help determine overall effectiveness. In elderly patients with epilepsy, the likelihood of polytherapy, along with physiological changes associated with aging, can make pharmacokinetic issues even more significant. One aspect of pharmacokinetics that has received less attention is the process of oral drug absorption. Aging can have variable effects on the gastrointestinal system. Some of these physiological changes have the potential to impact absorption patterns of some medications, including AEDs. Altered oral protective reflexes, xerostomia, and delayed esophageal emptying in elderly patients may complicate oral administration of some medications. Altered gastric pH could modify drug absorption, and modified gastric emptying rates can influence the bioavailability of some AEDs. Finally, intestinal transit times may be slower in elderly patients compared to younger patients, possibly altering the absorption of some AEDs. These age-related physiological changes that may affect AED pharmacokinetics should be considered when treating elderly patients with epilepsy.

Absorption↗
PubMed2004

Biopharmaceutic and pharmacokinetic aspects of variable bioavailability of rifampicin.

Even today the treatment outcome of tuberculosis is questionable due to variable bioavailability of rifampicin, which was discovered four decades back. In this manuscript, results of bioequivalence trials reported are presented in the form of a figure that provides a comprehensive look at the rifampicin bioavailability literature, provides understanding of the problem and clears 'myths and assumptions' regarding rifampicin bioavailability from fixed-dose combination (FDC) formulations. It was found that FDCs of good as well as bad quality rifampicin containing formulations with reduced or increased relative bioavailability are available. In addition, 'rifampicin alone' formulations also show variability in bioavailability. In the context of anomalous bioavailability of rifampicin, reasons postulated in literature are summarized. Approaches needed to solve the issue of rifampicin bioavailability are discussed on the basis of LADMER and BCS.

Antibiotics, Antitubercular↗
PubMed2004

The role of biopharmaceutics in the development of a clinical nanoparticle formulation of MK-0869: a Beagle dog model predicts improved bioavailability and diminished food effect on absorption in human.

MK-0869 (aprepitant), a potent substance P antagonist, is the active ingredient of EMEND which has recently been approved by the FDA for the prevention of chemotherapy-induced nausea and vomiting. Early clinical tablet formulations of MK-0869 showed significant food effects on absorption, suggesting that formulation could have a significant role in improving bioavailability. A Beagle dog model was developed in an effort to guide novel formulation development. Using the suspension of the micronized bulk drug used for the tablet formulations, the food effect on absorption was confirmed in the dog at a similar magnitude to that observed in humans. Further dog studies demonstrated a clear correlation between particle size and in vivo exposures, with the nanoparticle (NanoCrystal) colloidal dispersion formulation providing the highest exposure, suggesting dissolution-limited absorption. The NanoCrystal dispersion also eliminated the food effect on oral absorption in the dog at a dose of 2mg/kg. Regional absorption studies using triport dogs indicated that the absorption of MK-0869 was limited to the upper gastrointestinal tract. These results provided strong evidence that the large increase in surface areas of the drug nanoparticles could overcome the narrow absorption window and lead to rapid in vivo dissolution, fast absorption, and increased bioavailability. In addition, the dog model was used for optimizing formulation processes in which the nanoparticles were incorporated into solid dosage forms, and for selecting excipients to effectively re-disperse the nanoparticles from the dosage units. The human pharmacokinetic data using the nanoparticle formulation showed excellent correlations with those generated in the dog.

Absorption↗
PubMed2006

Biopharmaceutic and pharmacokinetic studies following the oral administration of sodium salicylate in oily and aqueous vehicles to rabbit.

The pharmacokinetic parameters, i.e. peak concentration (c(max)); peak time (t(max)); area under the curve (AUC); elimination rate constant (k); absorption rate constant (k(a)); Drug clearance (cl(t)), and the volume of distribution (v(d)) of sodium salicylate administered in fractionated coconut oil (FCO) have been compared with that from an aqueous and glycerin vehicles using a three-way crossover study in 12 rabbits. The results of the study show that all of the pharmacokinetic parameters tested differ significantly when administered in oily rather than aqueous or glycerin vehicles. No statistically significant difference was found between any of the above mentioned parameters when comparison was made between aqueous and glycerin formulations. The results indicate that sodium salicylate is absorbed at a lower rate but to a greater extent from oily formulation. Possible reasons for these differences are discussed and is suggested, therefore, that the oily formulation might be used as a sustained release preparation.

Administration, Oral↗
PubMed2006

Design of novel antifungal mucoadhesive films. Part II. Formulation and in vitro biopharmaceutical evaluation.

This paper deals with the formulation of the mucoadhesive films containing nystatin. The design and formulation of the films were based on the mucoadhesive properties of carbomer 934P (CB) and carboxymethycellulose (NaCMC), and also on the plasticizer properties of polyethyleneglycol 400 (PEG400). A surfactant (ascorbyl palmitate, ASC16) was added to the system to aid in nystatin dispersion. Addition of these last two components produced a significant improvement in physical-mechanical properties (flexibility and strength) as well as an increase in the nystatin release rate. X-ray powder diffraction (XRPD) and scanning electronic microscopy (SEM) were used to evaluate the morphological changes in the films while PEG400 and ASC16 were added to the formulations. Furthermore, the in vitro nystatin profile release was determined.

Acrylic Resins↗